With the shopping season just around the corner, it's a good bet you'll buy at least a few gifts via your iPhone. But if you download retailer apps, be prepared for varied experiences in response time, availability and consistency, according to Gomez, the Web performance division of Compuware.Gomez just released benchmarks of 15 iPhone apps from major retailers such as Amazon, Walmart, Target, Victoria Secret, Macy's, Apple, and others. The key finding: There's a huge discrepancy in the performance of these apps."There's a big gap between the fastest and the slowest simply because there isn't necessarily a full consensus over the expectations of what a native app should look like from an end-user perspective," says Imad Mouline, CTO at Gomez.Target's iPhone app, for instance, led the field with a response time of less than a second, while the average was more than four seconds.Gomez also measured an app's consistency, which is the standard deviation of the response time of completed transactions. Amazon's iPhone app had a consistency of 0.676 seconds, compared to Best Buy's 10.645 seconds.What's the problem? "Some retailers are simply putting a wrapper around their mobile optimized sites, while others are building a native app from the ground up," Mouline says. "That's one of the reasons why you have a disparity from both a look and feel and performance perspective."Retailer Apps: A Turn in the Road\nOnly a few years ago, the iPhone sent nearly every retailer with a website scurrying to build a mobile optimized website version. "The full Safari engine is inside of iPhone," Apple CEO Steve Jobs said back in 2007. "You can write amazing Web 2.0 and AJAX apps" that run in the Safari app. \nBy the beginning of 2010, there were 326,600 mobile websites, according to Taptu, a mobile search engine. "By the end of 2010, we forecast that the mobile touch web will have grown to more than 500,00 sites," says Steve Ives, CEO of Taptu, told CIO.com.\nThen the race to the mobile optimized website began to show mixed signs. Earlier this year, Jobs made it clear that he felt that iPhone users get data on the Internet through apps, not generalized Web search. Wired magazine echoed this sentiment last summer in its feature story, "The Web is Dead, Long Live the Internet."\nThe message seemed to be that the mobile browser and, consequently, mobile optimized websites have melted into the background as iPhone apps take center stage. Even the iPad renders standard websites beautifully, so who needs a mobile website anymore?\nRetailers that performed well in the Gomez benchmark often built a native app from scratch. They might have cached a lot of the data required for startup so that the app launches quickly. Or they might have added functionality such as geo-location and bar code scanning via the iPhone camera. \nBack to the Mobile WebsiteOther retailers have been reluctant to embrace the iPhone app, rather merely cloaking their mobile optimized website in an iPhone app wrapper. "One of the big drawbacks of a native app is what we call 'friction,' which basically means that in order for people to use the app, they have to go through the trouble of logging into an app store and downloading it," Mouline says. Mobile websites, on the other hand, have much lower friction from a customer's perspective. A shopper can visit a mobile website on Safari easily and without any obligation to access the retailer's content.But most retailers simply wrap their mobile websites to look like an iPhone app rather than tuning the mobile website for the iPhone. This often leads to poorer performing iPhone apps\u2014a potential death knell in the mobile retailer space."Once you have an app that's out there and in the hands of people, it has to work," Mouline says. "It's very hard to get a lot of people back after a bad [shopping] experience." Tom Kaneshige covers Apple and Networking for CIO.com. Follow Tom on Twitter @kaneshige. Follow everything from CIO.com on Twitter @CIOonline. Email Tom at firstname.lastname@example.org.